A home network system is a system for controlling household appliances, such as, PC, cellular phone, refrigerator, or washing machine, by one network.
In fact, the plural appliances are interconnected through a home bus, and to do so, a protocol, which is capable of integrating many signals for each appliance and controlling the signals, is absolutely necessary. One of typical examples of the protocol is CSMA/CD.
The most essential element in the CSMA/CD system is to create more effective communication in spite of some possible collisions that are generated as several appliances use one single home bus.
FIG. 1 is a diagram of a known collision detection method in CSMA/CD system.
Referring to FIG. 1, if a peripheral apparatus (it is used interchangeably with peripheral apparatus) has data to transmit, the peripheral apparatus generates a packet data and then waits until a home bus is in an idle state. Once the home bus is in the idle state, the peripheral apparatus performs a busy check, that is, the apparatus checks whether the home bus has been idle continuously for a certain amount of time. Here, the busy check time period is set equally for every appliance.
At the result of the busy check, if the home bus is currently in the idle state, the data is transmitted to a corresponding appliance through the home bus, while if it turns out that the home bus is currently in the busy state, the transmission is delayed for a certain amount of time, and after that, the busy check conducted again.
In this manner, a plurality of peripheral apparatus can transmit data to one single home bus simultaneously.
However, the method has a drawback as follows.
For example, FIG. 2 is a diagram illustrating some problems with the collision detection method based on a conventional CSMA/CD system.
As shown in FIG. 2, suppose that a first transmission apparatus and a second transmission apparatus are ready to transmit data at the same time, and perform the busy check on the home bus in the idle state. In such case, since the data transmission from each apparatus is done simultaneously in a certain amount of time upon finishing the busy check, there is a lot of collision in the home bus, and as a result thereof, transmission error occurs.